Process for refining cottonseed oil



Patented May 1, 1951 PROCESS FOR REFINING COTTONSEED OIL Willy Lange, Cincinnati, Ohio, assignor to The Procter and Gamble Company, Ivorydale, Ohio,

a corporation of Ohio No Drawing. Application September 19, 1949, Serial No. 116,610

Claims.

The present invention relates to the refining of crude cottonseed oil, and more particularly to the removal of free fatty acid and other undesirable impurities from crude cottonseed oil, by treatment with aqueous solutions of sodium hydroxide.

The alkali refining of crude cottonseed oil is an old art basically involving mixing an aqueous solution of sodium hydroxide with the oil to neutralize free fatty acid, precipitate mucilaginous material and remove coloring matter and other undesirable impurities along with the soap formed in the neutralization procedure. The precipitate thus formed is commonly referred to in the art as foots. In addition to impurities and excess sodium hydroxide solution, the foots contain a considerable proportion of neutral oil which is emulsified in the foots and carried down therewith. This neutral oil has only foots value and represents both an appreciable loss in the yield of neutral oil and a corresponding increase in refinin expense.

It is an object of my invention to reduce the loss of neutral oil in the alkali refining of crude cottonseed oil.

Numerous procedures have been proposed in the past for effecting reduction in the loss of neutral oil, the most promising procedure thus far developed being the continuous method wherein the separation of foots from the refined oil is eifected centrifugally rather than by gravity. Even in such centrifugal procedures there is an appreciable amount of neutral oil held up by the foots due to emulsification, and although the process of my invention is of particular value in the reduction of the refining loss in batch procedures employing gravity separation of the foots, the invention may be used to I advantage in the further reduction of losses in centrifugal procedures.

I have found that the properties of those substances which effect emulsification of neutral oil in the foots may be markedly changed by the incorporation of salicylic acid in the crude oil prior to the addition of the refining lye whereby the amount of neutral oil so emulsified in the foots is materially reduced. In accordance with my invention, the crude oil is first treated with the salicylic acid in'particulate iorm following which the crude oil is refined in the usual way with sodium hydroxide solution. I have found, however, that the action of the salicylic acid appears to be enhanced if a small amount of water is incorporated with the mixture of crude oil and salicylic acid before the addition of the lye.

As will be noted from the following detailed description, the essential distinguishing feature of the refining procedure of my invention over those hitherto employed is in the treatment of the crude oil with the salicylic acid, preferably in combination with the step of incorporating water in the mixture of crude oil and salicylic acid, prior to the addition of the refining lye.

As in hitherto employed refinin procedures, the concentration and amount of refining lye and the temperature of refining will vary depending on the proportion and kind of minor constituents contained in the oil. Higher concentrations are preferably used when the concentration of free fatty acid and color constituents in the crude oil is high. However, necessary adjustments to compensate for such variations in oil constitution are known to those versed in the art and have no influence on the advantages of using the salicylic acid in accordance with my invention. It is to be observed, however, that in the preferred method involving the incorporation of water with the mixture of crude oil and salicylic acid prior to the addition of the lye, the amount of water added should be compensated for by an increase in the concentration of sodium hydroxide solution used in the neutralization step.

The following examples will illustrate the manner in which my invention may be practiced, but it is to be understood that the procedures therein described are merely illustrative and are not intended to be limiting.

Example 1.Crude cottonseed oil having a free fatty acid content of 0.9% was mixed for 5 minutes with 0.01% of salicylic acid crystals. Thereafter 1% of water was added to the mixture and agitation was continued for 15 minutes.

The thus treated crude oil in admixture with the salicylic acid and water was mixed with 6.1% of 9.3% sodium hydroxide solution. After 15 minutes, agitation was reduced and the mixture was heated to about F. After the foots were in coagulated form, agitation was discontinued and the foots were allowed to settle by gravity. The loss noted was 5.5% whereas the loss obtained in refining the crude cottonseed oil in accordance with the same method without the use of salicylic acid or water but with 7.1 of 8% sodium hydroxide solution was 7.3%. A 24% reduction in loss was therefore obtained.

It is to be noted that here, as well as in succeeding examples wherein procedures are directly compared, the amount of actual sodium hydroxide used in refining is substantially the same in each of the procedures of the comparison.

Example 2.-Crude cottonseed oil containing 2.3% free fatty acid was refined batchwise in the normal way with 9.9% of 8% sodium hydroxide solution. The loss obtained was 7.0%.

The same crude cottonseed oil was intimately.

mixed at 75 to 80 F. with 0.1% (based on the weight of the oil) of salicylic acid crystals for 5 minutes. 9.9% of 8% sodium hydroxide solution was then added without previous addition of water and the refining was completed in the normal way. The loss obtained was 6.4%.

When the same crude oil was similarly treated with salicylic acid, and water was incorporated in the mixture before the addition of the sodium hydroxide solution, a, further reduction in the refining loss was, observed. Thus intimate admixture with 0.1% water for minutes resulted in a refining loss of 5.7%, and intimate admixture with 1% water for a similar period of I time resulted in a refining loss of 5.4%.

Example 3.Crude cottonseed oil containing 1.2% free fatty acid was refined batchwise in the normal way with 7.7% of 8% sodium hydroxide solution. The refining loss noted was 6.4%.

The same crude cottonseed oil was intimately mixed at 75 to 80 F. with 0.2% salicylic acid crystals for 5 minutes, following which the mixture was intimately contacted with 1% water by mechanical agitation for 15 minutes, then refined with sodium hydroxide solution, the amount of sodium hydroxide employed being substantially the same as that used previously, but the concentration being increased to compensate for added water. The refining loss observed was 5.1%.

Example 4.The invention is also applicable to crude cottonseed oils containing relatively high proportions of free fatty acid, as will be observed from the following.

Crude cottonseed oil containing 6% free fatty acid was refined batchwise in the normal way with 11% of 14% sodium hydroxide solution. The refining loss was 14.6%.

When this same crude oil was refined under comparable conditions using 0.1% salicylic acid crystals or 0.05% of salicylic acid, ground with oil to form a slurry, 1% water being added to the mixture and admixed therewith for 15 minutes before the addition of the refining lye, the refining loss was 10.8%.

As will be noted from the above examples, marked improvement in refining loss is obtained when the amount of salicylic acid employed is as low as 0.01% based on the weight of the oil. In some instances smaller amounts may be employed to advantage and in other instances the use of larger amounts may be desirable. However, more than 2% of salicylic acid is uneconomical because the decrease in loss is not always proportional'to the increase in salicylic acid employed.

Intimate contact of the salicylic acid with the crude oil shouldbe effected and the time of mixing will therefore vary depending on the size of the batch of oil being refined, the violence of agitation, etc. After intimate contact has been established, further agitation for at least one minute, preferably for not less than 5 minutes, is desirable.

As indicated in most of the examples, the salicylic acid may be added in crystalline form, but I have found that when the surface area of the salicylic acid crystals is increased about eight times by powdering or by grinding in oil to form a slurry, then the use of about 0.05 per cent salicylic acid gave about the same refining loss reduction as the use of 0.1 per cent salicylic acid crystals.

The amount of water that is employed in the preferred operation of my invention is not critical, but it is preferable that at least 0.1 per cent be used. Amounts up to 5 per cent may be employed in someinstances, depending on the character of the oil, but the use of greater quantities than 5 per cent effects little if any improvement. In fact such large quantities must be used with care-because of the danger of adversely affecting the refining loss.

In batch operations the mixing time may vary, for example, from 5 to 30 minutes. One per cent water admixed with the cottonseed oil and salicylic acid for 15 minutes has been found to give optimum results in most instances of batch operation.

In the examples, I have set forth a specific method for carrying out the neutralization procedure after treatment of crude oil with the salicylic acid in accordance with my invention. It is to be understood, however, that I am not limited to the particular method of neutralization and separation of the refined oil from the foots. These procedures may be varied appreciably, depending on the type of oil being refined, and variations in procedure, with which those versed in the art are familiar, may be readily substituted without departing from the spirit of the invention.

Moreover, although the specific description of the invention has been related to batch refining primarily because the greatest reduction in refining loss is noted in such batch procedures, it is to be understood that my invention may be used to advantage in continuous refining procedures employing continuous mixing of the constituentsadded to the oil, followed by continuous centrifugal separation of the refined oil and precipitated foots.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In the process of refining crude cottonseed oil involving the steps of neutralizing free fatty acid with an aqueous solution of sodium hydroxide wherein minor impuritie are precipitated as facts, and of separating refined oil from the foots, the step of agitating the crude oil with salicylic, acid in particulate form prior to the addition of sodium hydroxide solution.

2. Process of claim 1 in which the amount of salicylic acid is from about 0.01 per cent to about 2 per cent based on the weight of the oil.

3. The process of refining crude cottonseed oil which comprises agitating the crude oil with salicylic acid in particulate form, adding water to the mixture of crude oil and salicylic acid, then adding an aqueous solution of sodium hydroxide to neutralize the free fatty acid in the oil and precipitate minor impurities contained acid is intimately mixed with the crude oil for 10 at least one minute before adding the water, and in which the Water i intimately mixed with the t) crude oil and salicylic acid for from about 5 to about 30 minutes before adding the aqueous soluof sodium hydroxide.

WILLY LANGE.

REFERENGES CITED The following refei'enecs are of record in the file of this patent:

UNITED S'I'AIES PATENTS Name {Date Baxter -i Jan. 6, 1942 Number 

1. IN THE PROCESS OF REFINING CRUDE COTTONSEED OIL INVOLVING THE STEPS OF NEUTRALIZING FREE FATTY ACID WITH AN AQUEOUS SOLUTION OF SODIUM HYDROXIDE WHEREIN MINOR IMPURITIES ARE PRECIPITATED AS FOOTS, AND OF SEPARATING REFINED OIL FROM THE FOOTS, THE STEP OF AGITATING THE CRUDE OIL WITH SALICYCLIC ACID IN PARTICULATE FORM PRIOR TO THE ADDITION OF SODIUM HYDROXIDE SOLUTION. 